1. Field of the Invention
The present invention relates to a cordless telephone terminal controlling system and, more particularly, to a controlling system for a cordless telephone terminal which is provided with both a function of a handset of a wire telephone and a function of a multi-zone type cordless telephone terminal.
2. Description of the Related Art
There are two types of cordless telephones according to the usage thereof. One is a cordless home telephone and the other is a cordless office telephone.
The cordless home telephone is composed of a master phone (wire telephone) and a secondary phone (cordless terminal). The master phone is connected to an exchange by a wire and provided with a charging rest for receiving the secondary phone. When the secondary phone is separated from the charging rest, the master phone can transmit to and receive signals from the secondary phone on a radio wave.
Communication is possible on such a cordless home telephone by (1) lifting the handset of the master phone and inputting the telephone number of the called party by the key operation on the master phone, (2) operating a predetermined key on the master phone without lifting the handset and thereafter inputting the telephone number of the called party, (3) lifting the secondary phone from the charging rest and inputting the telephone number of the called party by the key operation on the secondary phone, or (4) operating a predetermined key on the secondary phone when it is not on the charging rest and thereafter inputting the phone number of the called party by the key operation on the secondary phone.
When an incoming call terminates at the cordless home telephone, it is possible to talk with the caller by (1) lifting the handset of the master phone, (2) lifting the secondary phone from the charging rest, or (3) operating a predetermined key on the secondary phone when it is not on the charging rest.
The multi-zone type cordless office telephone enables a person carrying the telephone to transmit and receive at any place in the office. FIG. 19 shows a structure of a conventional multi-zone type cordless telephone system. The reference numeral 1 represents a PBX (Private Branch Exchange), 2.sub.1, 2.sub.2 and 2.sub.3 denote cordless connecting devices, 3.sub.1, 3.sub.2 and 3.sub.3 cordless telephones, and 4.sub.1, 4.sub.2 and 4.sub.3 designate telephones (wire telephones) installed on desks.
The cordless connecting devices 2.sub.1, to 2.sub.3 transmit and receive signals to and from the cordless telephones 3.sub.1, 3.sub.2 and 3.sub.3 by transmitting a outgoing call signal, a incoming call signal and a speech signal on a radio wave, so that the range in which the radio wave is received is limited. For this reason, each of the cordless connecting devices 2.sub.1, 2.sub.2 and 2.sub.3 is installed, for example, on each of the first to third floors of a building BL so that the plurality of cordless connecting devices 2.sub.1, 2.sub.2 and 2.sub.3 cover the entire part of the building BL (the entire telephone service area). The range in which a radio wave from one cordless connecting device can be received is called a zone. The multi-zone type cordless telephone system is composed of a plurality of zones #1 to #3, so that transmission and reception are possible by the each of the cordless telephones 3.sub.1, 3.sub.2 and 3.sub.3 in any of the zones #1 to #3.
For example, in FIG. 19, the cordless telephone 31 on the first floor can transmit call signal through the cordless connecting device 2.sub.1 installed on the first floor, and when the cordless telephone 3.sub.1 is carried to the third floor, it transmits call signal through the cordless connecting device 2.sub.3. In addition, in the multi-zone type cordless telephone system, the PBX 1 registers the position of each cordless telephone so as to know in which zone each cordless telephone is located and to make the transmission to each cordless telephone smooth. For this purpose, the PBX 1 has a telephone number-zone table TLZ in which telephone numbers are listed in correspondence with the zones in which the cordless telephones having the respective telephone numbers are located. In the state shown in FIG. 19, if an incoming call is terminated at the cordless telephone 3.sub.3 having a number of 3000, the PBX 1 supplies an incoming call signal only to the cordless connecting device 2.sub.3 on the third floor to enable smooth reception by the cordless telephone 3.sub.3 having a number of 3000 on the third floor.
FIG. 20 is a flowchart of the process for registering, in the PBX 1, the zone in which each cordless telephone is located.
In the multi-zone type cordless telephone system, if the PBX 1 does not seize the zone in which each cordless telephone is located, it is impossible to call the corresponding cordless telephone smoothly. For this reason, each cordless connecting device 2i which is not occupied by a call periodically emits a radio wave with the number of the zone (zone identifier) to which it belongs to the cordless telephones in the same zone (101 and 102). When each cordless telephone 3i receives the zone number from the cordless connecting device 2i in the zone in which the cordless telephone 3i exists (step 103), the cordless telephone 3i judges whether or not the zone number stored in its memory portion agrees with the zone number received (step 104), and if the answer is YES, the process is returned to the step 101, and the processing thereafter is repeated. If the answer is NO, it means that the cordless telephone 3i is moved to another zone, so that the zone number in the memory is replaced by the zone number received (step 105). In this way, each cordless telephone 3i constantly holds the number of the zone in which it exists in its memory portion. Thereafter, the cordless telephone 3i transmits a position register signal which includes the telephone number and the latest zone number to the cordless connecting device 2i in that zone on a radio wave (step 106). When the cordless connecting device 2i receives the position register signal from the cordless telephone 3i, it supplies the signal to PBX 1 (step 107). The PBX 1 updates the telephone number-zone table TLZ in accordance with the position register signal (step 108) and waits for the next signal transmission. That is, the zone number corresponding to the telephone number received is updated with the zone number received.
To state this specifically, if the cordless telephone 3.sub.1 is in the zone #1, for example, the cordless telephone 3.sub.1 receives the zone number #1 from the cordless connecting device 2.sub.1 and stores it in the memory portion. In this state, if the cordless telephone 3.sub.1 is moved to the third floor, the cordless telephone 3.sub.1 receives the zone number #3 from the cordless connecting device 2.sub.3. Since the zone number stored in the memory portion is #1, there is discrepancy in zone number. In this case, the cordless telephone 3.sub.1 judges that it is moved to a different zone and updates the contents of the memory portion and simultaneously transmits a position register signal (including the telephone number 1000 and the zone number #3) to the cordless connecting device 23. When the cordless connecting device 2.sub.3 receives the position register signal, it transmits the signal to the PBX 1, and the PBX 1 updates the telephone number-zone table TLZ in the memory la so as to indicate that the cordless telephone 3.sub.1 having the telephone number of 1000 exists in the zone #3.
However, a conventional multi-zone type cordless telephone system is disadvantageous in that the cordless telephone cannot be used in the same way as a cordless home telephone.
In addition, in a multi-zone type cordless telephone system, the telephone number of the cordless telephone is different from the telephone number of a wire telephone installed on a desk. Therefore, the owner of a cordless telephone (1) informs callers of the telephone number of the cordless telephone in advance as well as the telephone number of the wire telephone installed on his desk, and asks the callers to call him up again on the cordless telephone when he is not at the desk, or (2) registers the telephone number of the cordless telephone to which the incoming call is to be transferred in his absence in the wire telephone on the desk and receives the transferred incoming call on the cordless telephone carried by him. Both of these methods are, however, inconvenient. In the method (1), callers must know two telephone numbers, and in the method (2), although the owner has only to tell callers the telephone number of the wire telephone on the desk, it is necessary to register the telephone number of the cordless telephone in the wire phone on the desk so that the incoming call in his absence to be transferred to the cordless telephone.